Mixed signal designs include an analog design section and a digital design section, and are typically targeted for a specific purpose and function. Due to a mixed signal design's complex nature, a mixed signal design typically requires a high level of expertise and careful use of design verification tools, which start at design description and continue through various abstraction levels until reaching device fabrication.
Mixed signal design verification presents unique challenges. Systematic design methodologies in the analog and mixed-signal arena are typically more primitive than digital design methodologies. As such, analog circuit design and verification automation is not available to the same extent as existing digital circuit design and verification automation.
In addition, combining analog designs with digital designs adds additional complexities and challenges. Analog mixed signal designs are typically verified using SPICE simulations and visual inspections of two or more models to verify equivalence. As such, analog mixed signal verification techniques are typically error prone and inadequate, especially in the area of detecting bugs due to discrepancies between a reference model (e.g. an RTL model) and a model under verification (e.g. schematic/transistor level model).